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361.
Use of stable nitrogen isotope ratios is one method that has been proposed to indicate anthropogenic nutrient enrichment in estuarine systems. However, the role of stable isotopes as a tool in long-term ecosystem monitoring has not been fully developed. Resident producer and consumer species were collected from marshes dominated by Spartina alterniflora and subject to a range of anthropogenic impacts in Cape Cod, Massachusetts, and in Great South Bay and Jamaica Bay, New York. Tissue isotope ratios of Spartina alterniflora, Ulva lactuca, Fundulus heteroclitus, and Geukensia demissa were analyzed in order to determine which organisms are the most sensitive indicators of changes in anthropogenic nitrogen source and loading. Power analysis was used to determine the sample sizes necessary to detect change in nutrient source using the species sampled. Relationships between the delta15N values of the species sampled and watershed population density and residential development were evaluated. Population density was a better indicator of anthropogenic nitrogen impact than residential development, since most anthropogenic nitrogen in the study marshes was derived from wastewater. Consumer species demonstrated lower within-site variability than producer species and would therefore require smaller sample sizes to detect changes in nitrogen source and loading. 相似文献
362.
Direct and interactive effects of enemies and mutualists on plant performance: a meta-analysis 总被引:5,自引:0,他引:5
Morris WF Hufbauer RA Agrawal AA Bever JD Borowicz VA Gilbert GS Maron JL Mitchell CE Parker IM Power AG Torchin ME Vázquez DP 《Ecology》2007,88(4):1021-1029
Plants engage in multiple, simultaneous interactions with other species; some (enemies) reduce and others (mutualists) enhance plant performance. Moreover, effects of different species may not be independent of one another; for example, enemies may compete, reducing their negative impact on a plant. The magnitudes of positive and negative effects, as well as the frequency of interactive effects and whether they tend to enhance or depress plant performance, have never been comprehensively assessed across the many published studies on plant-enemy and plant-mutualist interactions. We performed a meta-analysis of experiments in which two enemies, two mutualists, or an enemy and a mutualist were manipulated factorially. Specifically, we performed a factorial meta-analysis using the log response ratio. We found that the magnitude of (negative) enemy effects was greater than that of (positive) mutualist effects in isolation, but in the presence of other species, the two effects were of comparable magnitude. Hence studies evaluating single-species effects of mutualists may underestimate the true effects found in natural settings, where multiple interactions are the norm and indirect effects are possible. Enemies did not on average influence the effects on plant performance of other enemies, nor did mutualists influence the effects of mutualists. However, these averages mask significant and large, but positive or negative, interactions in individual studies. In contrast, mutualists ameliorated the negative effects of enemies in a manner that benefited plants; this overall effect was driven by interactions between pathogens and belowground mutualists (bacteria and mycorrhizal fungi). The high frequency of significant interactive effects suggests a widespread potential for diffuse rather than pairwise coevolutionary interactions between plants and their enemies and mutualists. Pollinators and mycorrhizal fungi enhanced plant performance more than did bacterial mutualists. In the greenhouse (but not the field), pathogens reduced plant performance more than did herbivores, pathogens were more damaging to herbaceous than to woody plants, and herbivores were more damaging to crop than to non-crop plants (suggesting evolutionary change in plants or herbivores following crop domestication). We discuss how observed differences in effect size might be confounded with methodological differences among studies. 相似文献
363.
Stavins Robert; Carraro Carlo; Kolstad Charles 《Rev Environmental Economics and Policy》2007,1(2):169-170
We are pleased to introduce this second issue of the Reviewof Environmental Economics and Policy. Like every issue, thisone includes several articles, a focused symposium, and a setof regular features. In the first of three articles, John Graham describes "The EvolvingRegulatory Role of the U.S. Office of Management and Budget,"where he was the "regulatory czar" as administrator of the Officeof Information and Regulatory Affairs (OIRA) from 2001 to 2006.In his essay, Graham responds to the perception of OMB as antiregulatoryby describing the history of OIRA's proactive 相似文献
364.
365.
Towards a framework for assessment and management of cumulative human impacts on marine food webs
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Sylvaine Giakoumi Benjamin S. Halpern Loïc N. Michel Sylvie Gobert Maria Sini Charles‐François Boudouresque Maria‐Cristina Gambi Stelios Katsanevakis Pierre Lejeune Monica Montefalcone Gerard Pergent Christine Pergent‐Martini Pablo Sanchez‐Jerez Branko Velimirov Salvatrice Vizzini Arnaud Abadie Marta Coll Paolo Guidetti Fiorenza Micheli Hugh P. Possingham 《Conservation biology》2015,29(4):1228-1234
Effective ecosystem‐based management requires understanding ecosystem responses to multiple human threats, rather than focusing on single threats. To understand ecosystem responses to anthropogenic threats holistically, it is necessary to know how threats affect different components within ecosystems and ultimately alter ecosystem functioning. We used a case study of a Mediterranean seagrass (Posidonia oceanica) food web and expert knowledge elicitation in an application of the initial steps of a framework for assessment of cumulative human impacts on food webs. We produced a conceptual seagrass food web model, determined the main trophic relationships, identified the main threats to the food web components, and assessed the components’ vulnerability to those threats. Some threats had high (e.g., coastal infrastructure) or low impacts (e.g., agricultural runoff) on all food web components, whereas others (e.g., introduced carnivores) had very different impacts on each component. Partitioning the ecosystem into its components enabled us to identify threats previously overlooked and to reevaluate the importance of threats commonly perceived as major. By incorporating this understanding of system vulnerability with data on changes in the state of each threat (e.g., decreasing domestic pollution and increasing fishing) into a food web model, managers may be better able to estimate and predict cumulative human impacts on ecosystems and to prioritize conservation actions. 相似文献
366.
C. Louise Goggin Patricia M. Please Malcolm J. Ridges Charles A. Booth Geoffrey R. Simpson Richard Green 《Local Environment》2017,22(10):1217-1236
Connecting people with nature improves well-being, but how people connect with natural places is not well documented. We asked 43 people (19 Aboriginal Australians, 24 non-Aboriginal people) about the messages they received from Country during an interactive experience in the remote Mungo National Park, Australia, and analysed the physical senses, emotions and cognitive processes they mentioned. The physical senses mentioned by most respondents were sight, hearing and motion (particularly walking). These senses helped people receive messages from Country and connect with place. We used the primary-process emotional systems of Panksepp [2010. Dialogues in Clinical Neuroscience, 12 (4), 533–545] as a framework to capture the emotional dimension of experience. Most people reported positive emotions; they spoke about being nurtured by the group and the land (CARE), and the intense joy (PLAY) of being part of the community, being on Country and being accompanied by Aboriginal people. However, our results indicate the framework does not capture the breadth of positive emotions, particularly those associated with connection to place and spiritual experiences. Both groups mentioned cognitive processes reflecting their beliefs, existing knowledge, or sharing and acquiring new knowledge. Our results indicate that the emotional dimension of experience has the potential to measure connection to place, and provide a subjective measure of well-being. More research is needed to document this dimension of experience, and how it changes with context. Our case study provides further insight for those who manage protected areas and seek to enrich the experience of visitors. 相似文献
367.
368.
An evaluation was conducted to establish the feasibility of a Natural Food Resources Bank (NFRB), in the form of forestry or grassland, to achieve both continuous food production and an accumulation of primary nutrients in living perennial plants. The development of an NFRB protects our living environment from deterioration (especially soil erosion) by increasing the surface coverage of the world's land, even in mountainous areas. Additionally a functioning NFRB enhances food sustainably and security, representing a tangible and renewable food resource production system. Research has identified the prospects of cultivating the NFRB in the form of forestry and also grassland. The review investigated the distinct differences of an NFRB from a range of approaches and discusses the environmental advantage and feasibility of cultivating NFRB. The ability of the NFRB to realize sustainable food resources production for ensuring food security is evaluated in terms of environmental and economical feasibility. A NFRB can attenuate climatic change by increasing CO2 absorption and fixation. It is worth considering the replacement of the annual food production system by the NFRB (especially in steeplands) in environmental law, and replacing the policy of maintaining annual food reserves by the NFRB in food security policy. 相似文献
369.
Dianne I. Greenfield Ashley Duquette Abby Goodson Charles J. Keppler Sarah H. Williams Larissa M. Brock Krista D. Stackley David White Susan B. Wilde 《Environmental management》2014,54(5):1110-1120
Toxic cyanobacteria blooms are a growing concern for public health and safety, due in part to the production of the hepatotoxin microcystin by certain species, including Microcystis aeruginosa. Management strategies for controlling cyanobacteria blooms include algaecide treatments, often with copper sulfate, and more recently oxidizers such as sodium percarbonate that produce hydrogen peroxide. This study assessed the effects of two copper-containing algaecides and one sodium percarbonate-containing algaecide on mitigating cell numbers and toxin content of cultured M. aeruginosa and summer (July) bloom samples of Anabaenopsis sp. in a brackish stormwater detention pond. Monitoring of the bloom revealed that Anabaenopsis sp. was associated with elevated levels of orthophosphate compared to nitrogen (dissolved inorganic nitrogen to phosphorus ratios were 0.19–1.80), and the bloom decline (September–October) was likely due to lower autumn water temperatures combined with potential grazing by the dinoflagellate Protoperidinium quinquecorne. Laboratory-based algaecide experiments included three dose levels, and cyanobacteria cell numbers and microcystin concentrations (particulate and dissolved) were evaluated over 7 d. Following exposure, copper-containing treatments generally had lower cell numbers than either sodium percarbonate-containing or control (no algaecide) treatments. Addition of algaecides did not reduce overall microcystin levels, and a release of toxin from the particulate to dissolved phase was observed in most treatments. These findings indicate that algaecide applications may visibly control cyanobacteria bloom densities, but not necessarily toxin concentrations, and have implications for public health and safety. 相似文献
370.
Craig F. Aumack Charles D. Amsler James B. McClintock Bill J. Baker 《Marine Biology》2011,158(8):1879-1885
Amphipods along the western Antarctic Peninsula appear to gain refuge from predators by associating with chemically defended
macroalgae rather than palatable macroalgae. However, nothing is known about amphipod activity at night. If foraging on non-chemically
defended macroalgae regularly occurs, then nocturnal foraging seems beneficial since visual predators are disadvantaged. To
test this hypothesis, we collected three common macroalgal species and affiliated mesograzers, approximately 3 h before and
after sunset. All associated mesofauna were counted and densities recorded. Amphipod densities were significantly decreased
during the night on the chemically defended Desmarestia menziesii, while significantly increased on the palatable Iridaea cordata. Additionally, the amphipod Gondogeneia antarctica was found in significantly higher densities at night on Palmaria decipiens, a species shown to be readily eaten by G. antarctica and omnivorous fish. We believe that chemically defended macroalgae act as a refuge for mesograzers during the day, while
more widespread foraging occurs at night. 相似文献